1. Field of the Disclosure
This disclosure relates generally to methods and apparatus for dispensing a viscous material on a substrate, such as a printed circuit board, and more particularly to a method and an apparatus for calibrating dispensing material on a substrate with enhanced efficiency.
2. Discussion of Related Art
There are several types of prior art dispensing systems used for dispensing precise amounts of liquid or paste for a variety of applications. One such application is the assembly of integrated circuit chips and other electronic components onto circuit board substrates. In this application, automated dispensing systems are used for dispensing very small amounts, or dots, of viscous material onto a circuit board. The viscous material may include liquid epoxy or solder paste, or some other related material.
In one system capable of dispensing dots of material, a dispenser unit comprises a housing having a chamber and a piston disposed in the chamber. The piston (also referred to herein as an actuator) is configured to move between a pre-dispense position and a dispense position within the chamber. A motor is coupled to the piston to drive the movement of the piston within the chamber. The dispenser unit further comprises a dispensing bore configured to receive the piston therein and a nozzle coupled to the housing. The nozzle has an orifice co-axial with the dispensing bore. A controller is coupled to the motor to control the operation of the motor and thus the movement of the piston. The dispenser is constructed such that a volume of viscous material dispensed through the dispensing bore is substantially equal to the volume of the piston entering the dispensing bore when moving the piston to the dispense position. One such system is disclosed in U.S. Patent Publication No. 2008/0105703, entitled “METHOD AND APPARATUS FOR DISPENSING A VISCOUS MATERIAL ON A SUBSTRATE,” which is owned by Illinois Tool Works, Inc. of Glenview, Ill., the assignee of the present invention, and which is incorporated herein by reference in its entirety.
Additionally, the dispensing system may be calibrated for accurately controlling the rate and amount of viscous material that is dispensed from the dispenser unit. For example, a quantity of material may be dispensed and weighed to determine if the unit is dispensing the desired amount of material for a given configuration of the system.